The measured input distributions contain correlated errors, which are parameterized by the
respective fits. cf. 
[1]}, [2]}, [3]}. Their evolution, including the corresponding correlation matrix,
has to be performed to provide
the error prediction of the structure function at every fixed value of \(\Lambda _{\rm QCD}, m_c\)  and \(m_b\) 
respectively. Here one may use the corresponding formulae for the correlated error propagation given in
Ref. [1]} and extensions of them, which are straightforward. Within future data analyses one
will probably import the values of the heavy quark
masses from the world data analyses. For the charm quark mass it has already been shown that its value obtained
from deep–inelastic scattering data fully agrees with other precision measurements [5]}.
In our illustrations we will use the values \(m_c = 1.59~\mathrm {GeV}\)  [5]} and \(m_b = 4.78~\mathrm {GeV}\)  [7]}.
